1. Field of the Invention
The present invention relates to a liquid crystal driving device, and more particularly to an impulsive type liquid crystal driving device which inserts black data during a vertical blanking interval and then realizes a motion picture.
The present invention is based on a system for displaying a motion picture by means of TFT-LCD (Thin Film Transistor Liquid Crystal Display) including a liquid crystal having a high response characteristic. In a liquid crystal driving device according to the present invention, a refresh rate may be set as 60 Hz in order to display the motion picture, but the refresh rate is not limited to that.
2. Description of the Prior Art
Generally, in a liquid crystal display device, an arrangement of liquid crystal molecules is changed by means of an electric field effect so that a light transmittance of the liquid crystal molecules is adjusted and thus an image is displayed. Further, liquid crystal display devices have developed from a TN-LCD type to a STN-LCD type, a MIM-LCD type and a TFT-LCD type, and display performance of liquid crystal display devices has remarkably improved. Since such liquid crystal display devices not only have low power consumption but also have compact sizes and small weights, they have attracted considerable attention as devices which can substitute for CRTs (Cathode Ray Tubes). Furthermore, as they have been widely utilized in notebooks and portable mobile communication devices, etc., demand for them has been on the rise.
A conventional liquid crystal driving device sequentially applies a gate on/off pulse from a first gate bus line to n-th gate bus line during one frame of a vertical sync (V_sync) and then sequentially scans the gate bus lines. Further, during an occurrence of a horizontal sync, the conventional liquid crystal driving device applies a data signal to each pixel of the gate bus line selected through a data bus line, and then displays one frame image by constantly maintaining the applied data signal. Such a liquid crystal driving method is called as “hold type”.
A gate driver IC utilizing gate sequential scanning method according to the prior art is shown in FIG. 1.
Referring to FIG. 1, the conventional gate driver IC includes a plurality of shift registers SR1˜SRn, a plurality of level shifters LS1˜LSn and a plurality of buffer amplifiers BF1˜BFn. The plurality of shift registers SR1˜SRn receives a vertical starting signal STV in response to a vertical clock signal CPV and then sequentially shifts it to a next terminal in order to output it. The plurality of level shifters LS1˜LSn are respectively coupled to the plurality of shift registers SR1˜SRn, level-convert the output signals of the plurality of shift registers SR1˜SRn and then output the level-converted signals. The plurality of buffer amplifiers BF1˜BFn amplify the signals level-converted by the plurality of level shifters LS1˜LSn and then output gate on/off signals G1˜Gn.
Generally, it is preferred that a response speed of a liquid crystal is approximately 5 ms in order to reproduce a motion picture, but the response speed of liquid crystals have not been faster than the processing speed of image information in hold type liquid crystal display devices. Therefore, blurring due to image information from a prior picture remaining in the next frame may occur, thereby causing the degradation of the picture quality.
In order to improve such problems, a liquid crystal driving device, which utilizes an impulsive driving method of performing high-speed driving after dividing one frame, the refresh rate of which is 60 Hz, into an active address interval and blanking interval of 120 Hz, has been proposed. Herein, the impulsive driving method assigns a predetermined interval as a black image space in a unit of one frame in order to prevent image information in a prior frame from affecting a current frame.
However, in the conventional impulsive driving method, the blurring can't be completely removed, the occurrence possibility of EMI (Electro-magnetic interference) is high and the data maintenance time of a liquid crystal during the active address interval is short.
Also, in a case in which TV signals such as NTSC and PAL are reproduced, since one frame interval has been fixed as 16.7 ms, when an active interval is driven at 85 Hz in a liquid crystal driving device having an XGA grade, an activation interval of a vertical clock signal CPV is 11.2 ms and an interval, in which black data can be inserted, is approximately 5.5 ms.
However, in the conventional liquid crystal display device as described above, since the gate sequential scanning method has been utilized, the black data can't be inserted during the short time of 5.5 ms even if all gates are driven.